Traffic handling in a protected synchronous communication network

Abstract

A method for dynamically adding a new channel to a group of virtually concatenated channels carrying traffic to a network element (NE) of a synchronous network. By this method if a delay associated with the new channel is longer than a delay associated with the group of virtually concatenated channels then traffic received along the group of virtually concatenated channels is delayed until the group of virtually concatenated channels and the new channel are time-aligned, and then the new channel is added to the group. If the delay associated with the new channel is shorter than the delay associated with the group of virtually concatenated channels then traffic in the new channel is delayed until the new channel and the group of virtually concatenated channels are time-aligned, and then the new channel will be added to the group.

1. A method for enabling communication between a first network element (NE) and a second NE of a synchronous network which is adapted to support dynamic application of changes to an aligned group of virtually concatenated channels carrying communication traffic between said first NE and said second NE, the method comprising:
 distinguishing between a first mode of time aligning said group of virtually concatenated channels following the addition of a new channel to said group in response to a failure event occurring in at least one of the channels belonging to said group, or following a detection that at least one of the previously aligned channels is not aligned with the remaining channels of the group and a second mode of time aligning said group when a new channel is added to the group or a selected channel is removed from the group in response to a request transmitted by a managing element, wherein
 in said first mode, the time alignment is performed without using any pointer justification action regardless of network delays associated with said group's channels, and 
 in the second mode, if a network delay associated with a new channel to be added to said group of virtually concatenated channels is longer than a network delay associated with said group, the time alignment of the new channel and the group is achieved by using at least one pointer justification action. 
 
 
     
     
       2. A method according to  claim 1 , and wherein if a network delay associated with a channel selected to be removed from said group of virtually concatenated channels is longer than a network delay associated with said group excluding the selected channel, the time alignment of the channels in the group other than the selected channel is carried out by using at least one pointer justification action. 
     
     
       3. The method according to  claim 1  and wherein said distinguishing step comprises:
 monitoring said communication traffic carried to along said group to obtain an indication that refers to the operability status of at least one channel in the group; and 
 determining the mode of time alignment to be carried based on information retrieved from said indication. 
 
     
     
       4. The method according to  claim 1  and wherein said distinguishing step comprises:
 monitoring said communication traffic carried along said group to obtain a request from a managing element that refers to an addition or a removal of at least one channel to or from said group of virtually concatenated channels. 
 
     
     
       5. The method according to  claim 3  and wherein said indication comprises at least one alarm signal. 
     
     
       6. The method according to  claim 1  and wherein said distinguishing step comprises the step of determining that addition of a new channel to the group is made according to the first mode if the new channel comprises a backup channel. 
     
     
       7. The method according to  claim 1  and wherein in the first mode, the at least one of the channels in the group in which said failure event occurs, carries communication payload comprised in said communication traffic. 
     
     
       8. The method according to  claim 7  and wherein in the first mode the new channel is added to the group in order to protect said communication payload carried along said at least one of the channels in the group. 
     
     
       9. The method according to  claim 1  and wherein in the second mode, the at least one pointer justification action used before addition of a new channel to the group if a network delay associated with the new channel is longer than a network delay associated with the group, comprises at least one positive pointer justification action. 
     
     
       10. The method according to  claim 1  and wherein in the second mode, the at least one pointer justification action used following removal of a selected channel from the group if a network delay associated with the group excluding the selected channel is shorter than a network delay associated with the selected channel, comprises at least one negative pointer justification action. 
     
     
       11. The method according to  claim 1  and wherein said synchronous network comprises at least one of the following: a network based at least partially on the Synchronous Optical Network (SONET); and a network based at least partially on the Synchronous Digital Hierarchy (SDH). 
     
     
       12. An apparatus for enabling communication between a first network element (NE) and a second NE of a synchronous network which is adapted to support dynamic application of changes to an aligned group of virtually concatenated channels carrying communication traffic between said first NE and said second NE, the apparatus comprising:
 a synchronous processor operative to receive said communication traffic carried along said group of virtually concatenated channels; and 
 a controller operatively associated with the synchronous processor and operative to control said synchronous processor for distinguishing between a first mode of changing the group in which a new channel is added to the group in response to occurrence of a failure event in at least one of the channels in the group, and a second mode of changing the group in which a new channel is added to the group or a selected channel is removed from the group not in response to occurrence of such a failure event, wherein 
 in said first mode, the synchronous processor is operative under control of the controller to perform time alignment of the new channel and the group without using any pointer justification action regardless of network delays associated with the new channel and the group, and 
 in the second mode, if a network delay associated with a new channel to be added to the group of virtually concatenated channels is longer than a network delay associated with said group, the addition of the new channel to the group is performed by the synchronous processor after time aligning the new channel and the group by using at least one pointer justification action. 
 
     
     
       13. An apparatus according to  claim 12 , wherein in the second mode, if a network delay associated with a channel selected to be removed from said group of virtually concatenated channels is longer than a network delay associated with said group excluding the selected channel, the removal of the selected channel from the group is performed by the synchronous processor by using at least one pointer justification action. 
     
     
       14. An apparatus according to  claim 12 , wherein in the first mode, said synchronous processor is operative under control of said controller to perform a hit process to achieve time alignment of the new channel and the group. 
     
     
       15. An apparatus according to  claim 12 , and said controller is operative to distinguish between the two modes of operation by monitoring the communication traffic carried along said group to obtain an indication that refers to the operability status of at least one channel in the group, and determining the mode of time alignment to be carried based on information retrieved from said indication. 
     
     
       16. An apparatus for enabling communication between a first network element (NE) and a second NE of a synchronous network which is adapted to support dynamic application of changes to a group of virtually concatenated channels carrying communication traffic between the first NE and the second NE, the apparatus comprising:
 a mapper/demapper unit operative to receive said communication traffic carried along said group of virtually concatenated channels; and 
 a controller operatively associated with the mapper/demapper unit and operative to control said mapper/demapper unit for distinguishing between a first mode of changing the group in which a new channel is added to the group in response to occurrence of a failure event in at least one of the channels in the group, and a second mode of changing the group in which a new channel is added to the group or a selected channel is removed from the group not in response to occurrence of such a failure event, wherein
 in the first mode, when a new channel is to be added to the group, the mapper/demapper unit is operative under control of the controller to perform time alignment of the new channel and the group without using any pointer justification action regardless of network delays associated with the new channel and the group, and 
 in the second mode, addition of a new channel to the group, if a network delay associated with the new channel is longer than a network delay associated with the group, is performed by the mapper/demapper unit after achieving time alignment of the new channel and the group by using at least one pointer justification action, and removal of a selected channel from the group, if a network delay associated with the group excluding the selected channel is shorter than a network delay associated with the selected channel, is followed by performance by the mapper/demapper unit of time alignment of channels in the group other than the selected channel by using at least one pointer justification action. 
 
 
     
     
       17. An apparatus according to  claim 16 , wherein in the first mode, said mapper/demapper unit is operative under control of said controller to perform a hit process to achieve time alignment of the new channel and the group.